Boiler

ABSTRACT

A boiler, usable for central heating, has at least one fire duct and, on either side thereof, ducts for a heat-transferring medium, normally water, the fire duct and the water ducts being formed by elements cast in one piece of an aluminum alloy. One side of the elements forms a component part of a fire duct and the other side a component part of the water duct, the elements being interconnected by welding.

United States Patent 1191 Giesen Dec. 31 1974 I 9 BOILER 71 35 3/ 3 l 1[75] Inventor: Gerardus Johannes Giesen, Tegelen, 4 233 Netherlands3,385,356 5/1968 Assigneez Beondu A.G., Vanduz, Liechtenstein Coley eta1 22 Pl d: Ma 21, 1973 1 I e y Primary ExaminerKenneth W. Sprague PP362,414 Attorney, Agent, or FirmAnthony A. OBrien [30] ForeignApplication Priority Data May 23, 1972 Netherlands 7206921 [57] ABSTRACTA boiler, usable for central heating, has at -least one 2 "122/367122/156 1 3 fire duct and, on either side thereof, ducts for a heat- 51I t C F225 3/7/10 transferring medium, normally water, the fire duct andd C 367 A the water ducts being formed by elements. cast in one 1 0 carel22/l 1 6 piece of an aluminum alloy. One side of the elements forms acomponent part of a the duct and the other side a component part of thewater duct, the elements [56] UNITE D S;T;:S SZ?FENTS beinginterconnected by welding.

533,395 1/1895 Page 122/367 10 Claims, 2 Drawing Figures PATENTEDDEB3 1m4 857.- 367 I saw 2 or 2 BOILER both dimension and form. Simple andrapid maintenance is also a matter of importance in the installment ofsuch a boiler in private dwellings.

It is an object of the invention to provide a boiler which fulfills allthe above-mentioned objectives.

According to the invention, there is provided a boiler preferably agas-fired central heating boiler, characterized by at least one fireduct adjoined on opposite sides by ducts which are connected in parallelfor circulating therethrough a heat-transferring medium, such as water,the fire duct and the water ducts being divided by heat conductingelements cast in one piece of an aluminium alloy, one side of whichdefines a border of the fire duct and the other side a border of thewater duct.

In a one-flue embodiment the boiler is therefore provided with onecentral fire duct and two ducts for the heat-circulating medium.

In previously known boilers the boiler elements or sections are cast ofcast iron or steel, using cores for forming the duct hollows. Not onlydoes this impose limitations in the design of the various ducts, becausethe cores used must be removable, but also sand residues from the corecasting process may be left in the water ducts, which cannot be removedafter casting. By constructing the heat transferring parts of the boilerout of a light metal in such a .way that one side thereof forms acomponent part of a fire duct and the other side a component part of awater duct, the water ducts and fire ducts can be adapted as much aspossible to the heat transfer desired at each point, at minimum castingcosts. The elements thus made can afterwards be secured by welding toform fire ducts and water ducts. Before welding, however, all surfacesare accessible to such an extent that any finishing operation, to obtaina desired surface texture for better heat exchange, can be carried out.The casting process without cores is particulary suitable formanufacturing boiler elements of light metal, for instance aluminiumalloy, which ensures greater heat exchange than a cast iron or steelpartition between a fire duct and a water duct.

Also according to the invention projections are formed on each fireduct-defining element on the fire duct side, the projections beingshaped and located to provide maximum heat transfer in a flame zone ofthe fire duct immediately above a burner bed and a combustion gas zoneof the fire duct located above th flame zone. the

Each fire duct wall is preferably completely covered with pyramid-shapedprojections in the flame zone. Each fire duct wall is preferably coveredin the gas zone with finger-shaped projections arranged in a pattern oflaterally staggered horizontal rows, the projections extending out tothe centre of the fire duct. Because these fingers contact each other inthe centre of the fire duct and are staggered transversely to thedirection of the gas flow, the combustion gases are forced to follow alabyrinth path in which turbulence accurs, which allows for good heattransfer. It is, for instance, possible with the boiler of the presentinvention to attain a gas temperature in the chimney of less than 200Cat a flame temperature of approximately l200C.

In the boiler according to the invention it is preferred that thefingers have a diamond-shaped cross-section with a ratio between thediagonals of between 1:2 and 1:4, preferably 113. The fingers arepreferably disposed with their longer diagonal in the direction of flowand with the distance or pitch between the fingers in each horizontalrow approximately equal to the length of the short diagonal.

To aid in the removal of cores at the end of the casting process thefingers of the fire duct wall are faintly tapered towards the centre,preferably, in a ratio of 102/100, the length of the long diagonal atthe smaller end being approximately l/lO of the length of the finger.

Each fire duct wall can also be provided with a system horizontallyextending baffles of equal height on the water duct side of the heatconducting elements, which baffles define, together with the walls ofthe boiler which theycontact a labyrinth-shaped water passage extendingover substantially the entire wall of the fire duct.

The water can be introduced to the water ducts at half the height of theboiler whenthe water ducts are connected in parallel and the path of thewater can be restricted so that the inflowing water is first carrieddownwards and then guided upwards along a zig-zag path.

The construction of the boiler of the invention is very simple: for itis composed of a small number of elements, for example, four; it has asmall width, and

' needs only one row of burners which are extremely easily accessiblefor maintenance purposes. The efficiency is nevertheless very high,because a light metalguaranteeing a high heat transfer is used, andbecause the specific casting process to be employed has made it'possibleto cover the fire duct and the 'water duct walls with an optimum numberof heat exchange promoting elements.

The completely symmetrical construction will also allow for adaptationto the space available for the boiler.

In a one-flue embodiment of the boiler according to the invention, theboiler dimensions being x 30 x 22 cm, a capacity of 30000 kcal/h isfeasible.

One embodiment of the boiler according to the invention will bedescribed by way of example with reference to the accompanying drawings,of which FIG. 1 is a side view of the boiler with some parts beingbroken away, and showing the upper portion slightly inclined towards thereader, and

FIG. 2 is a cross-sectional view on the line II-Il of FIG. 1.

As shown in FIG. 2, the boiler has four elements arranged in pairs,being mirrorsymmetric relative to one another. These elements are outercover plates 1 and 2 between which symmetrically disposed heatconducting elements 3 and 4 are located.

Elements 3 and 4, made of light metal, form partitions between a centralfire duct 5 and two water ducts 6 and 7.

The lower portion of fire duct 8 constitutes a flame zone, above which acombustion gas zone 9 is located. The walls of the fire duct in flamezone 8 are completely covered with pyramid-shaped projections 10, whilein the flame zone finger-shaped projections 11, 11 extend towards oneanother from each element 3, 4.

The finger-shaped projections are arranged on the respective fire ductwalls in a pattern of rows of fingers 11,11 extending transversely tothe movement of the combustion gas, the fingers being staggered insuccessive rows. As is shown in particular in the perspective view atthe upper portion in FIG. 1, the fingers have a diamond-shapedcross-section, the long diagonal of the diamond extending vertically,that is to say, in the direction of flow of thecombustion gases. Themutual distance between the fingers 11 and 11' in each row i.e., thepitch, is approximately equal to the length of the short diagonal andfingers 11 of the top row shown are horizontally staggered over thepitch distance relative to fingers 11 in the subjacent horizontal row.

Fingers l1 and 11' meet in the centre of the fire duct.

Baffles 12 extend into water ducts 6 and 7 and are integrally formed ofelements 3 and 4. Together with cover plates 1 and 2 the baffles definea labyrinth or zig-zag-shaped water passage, in which the water flowsfrom the bottom to the top. In the embodiment shown the water isintroduced through inlets 13 located approximately at half the height ofthe boiler, so that it first blows downwards and then follows themeandering path upwards as indicated by arrows W in FIG. 1.

The water can be supplied through a T-piece. Under the boiler a burner14 is located.

- it is obvious that the bottom of a boiler which is not of thegas-fired type can also be water-cooled.

We claim:

1. A boiler comprising a vertically extending outer wall,

a burner means,

two vertically extending heat conducting elements secured parallel toand at a distance inside of said outer wall,

a fire duct defined between said heat conducting ele ments, said burnermeans being located in'said fire duct, and

water ducts extending between said heat conducting elements and saidouter wall for circulating a heat transfering medium therethrough, v

each of saidheat conducting element being a single separately cast pieceof light metal.

2. A boiler as claimed in claim 1 wherein the ligh metal is an aluminumalloy.

3. A boiler as claimed in claim 2 wherein each heat conducting elementis provided with a plurality of horizontally-extending baffles, thebaffles extending into the water ducts and contacting said outer wall todefine zig-zag type paths for the water through said ducts.

4. A boiler as claimed in claim 3 wherein the water' an outer wallenclosed the boiler, vertical heat conducting elements each cast in onepiece of an aluminum alloy, the fire duct being defined between saidelements, the water ducts being defined between said elements and theouter wall, and finger shaped projections on the heat conductingelements extending into thecenter of the combustion gas'zone of saidfire duct to provide maximum heat exchange, said projections beingarranged in staggered horizontal rows.

6. A boiler as claimed in claim 5 wherein each finger shaped projectionhas a cross section in the form of a diamond having longer and shorterdiagonals, the ratio of the length of the longer and shorter diagonalsbeing between 2:1 and 4:1.

7. A boiler as claimed in claim .6 wherein the longer diagonals of thediamond shaped cross section of each projection are oriented verticallyand when each of the projections in each of the horizontal rows isseparated from the next by a distance equal to the length of the shorterdiagonal of the diamond.

8. A boiler as claimed in claim 6 wherein each of said projectionstapers slightly as it extends into the fire duct and wherein the lengthof the longer diagonal is approximately 1/10 the length of theprojection.

9. A boiler as claimed in claim 5 wherein aplurality of horizontallyextending baffles extend from each of said heat conducting elements intothe water ducts to water duct and is first conducted downward beforeentering the zig-zag type path.

1. A boiler comprising a vertically extending outer wall, a burnermeans, two vertically extending heat conducting elements securedparallel to and at a distance inside of said outer wall, a fire ductdefined between said heat conducting elements, said burner means beinglocated in said fire duct, and water ducts extending between said heatconducting elements and said outer wall for circulating a heattransfering medium therethrough, each of said heat conducting elementbeing a single separately cast piece of light metal.
 2. A boiler asclaimed in claim 1 wherein the light metal is an aluminum alloy.
 3. Aboiler as claimed in claim 2 wherein each heat conducting element isprovided with a plurality of horizontally-extending baffles, the bafflesextending into the water ducts and contacting said outer wall to definezig-zag type paths for the water through said ducts.
 4. A boiler asclaimed in claim 3 wherein the water is introduced to each water ductintermediate its length and is conducted downward therein beforeentering said zig-zag type path and wherein each of the water ducts isconnected in parallel with the other.
 5. A boiler comprising a verticalfire duct having a combustion gas zone and a flame zone containing aflame therein, a vertical water duct on either side of said fire duct,an outer wall enclosed the boiler, vertical heat conducting elementseach cast in one piece of an aluminum alloy, the fire duct being definedbetween said elements, the water ducts being defined between saidelements and the outer wall, and finger shaped projections on the heatconducting elements extending into the center of the combustion gas zoneof said fire duct to provide maximum heat exchange, said projectionsbeing arranged in staggered horizontal rows.
 6. A boiler as claimed inclaim 5 wherein each finger shaped projection has a cross section in theform of a diamond having longer and shorter diagonals, the ratio of thelength of the longer and shorter diagonals being between 2:1 and 4:1. 7.A boiler as claimed in claim 6 wherein the longer diagonals of thediamond shaped cross section of each projection are oriented verticallyand when each of the projections in each of the horizontal rows isseparated from the next by a distance equal to the length of the shorterdiagonal of the diamond.
 8. A boiler as claimed in claim 6 wherein eachof said projections tapers slightly as it extends into the fire duct andwheRein the length of the longer diagonal is approximately 1/10 thelength of the projection.
 9. A boiler as claimed in claim 5 wherein aplurality of horizontally extending baffles extend from each of saidheat conducting elements into the water ducts to contact the outer wallto define a zig-zag type path for the water through said duct.
 10. Aboiler as claimed in claim 9 wherein water is introduced at anintermediate level in the height of the water duct and is firstconducted downward before entering the zig-zag type path.